Process and apparatus for mixing two streams of catalyst

ABSTRACT

A process and apparatus for mixing streams of regenerated and carbonized catalyst involves passing a catalyst stream into and out of a chamber in a lower section of a riser. The chamber fosters mixing of the catalyst streams to reduce their temperature differential before contacting hydrocarbon feed.

BACKGROUND OF THE INVENTION

The invention relates to a process and apparatus for mixing carbonizedand regenerated catalyst. A field of the invention may be the field offluid catalytic cracking (FCC).

FCC is a hydrocarbon conversion process accomplished by contactinghydrocarbons in a fluidized reaction zone with a catalyst composed offinely divided particulate material. The reaction in catalytic cracking,as opposed to hydrocracking, is carried out in the absence ofsubstantial added hydrogen or the consumption of hydrogen. As thecracking reaction proceeds substantial amounts of highly carbonaceousmaterial referred to as coke are deposited on the catalyst to providecoked or carbonized catalyst. This carbonized catalyst is often referredto as spent catalyst. However, this term may be misconstrued because thecarbonized catalyst still has significant catalytic activity. Vaporousproducts are separated from carbonized catalyst in a reactor vessel.Carbonized catalyst may be subjected to stripping over an inert gas suchas steam to strip entrained hydrocarbonaceous gases from the carbonizedcatalyst. A high temperature regeneration with oxygen within aregeneration zone operation burns coke from the carbonized catalystwhich may have been stripped.

Although the carbonized catalyst carries coke deposits it may still haveactivity. U.S. Pat. No. 3,888,762 discloses mixing carbonized andregenerated catalyst for contact with the hydrocarbon feed. Theregenerated catalyst may be in the range of 593° to 760° C. (1100° to1400° F.) and the carbonized catalyst may be in the range of 482° to621° C. (900° to 1150° F.). U.S. Pat. No. 5,597,537 discloses mixing thecarbonized and regenerated catalyst in a blending vessel to allow theregenerated and carbonized catalyst to reach a temperature equilibriumbefore contacting the hydrocarbon feed. U.S. Pat. No. 7,935,314 B2discloses baffles in the riser to obstruct upward catalyst flow tofoster mixing. A mixed catalyst with more uniform temperature avoids hotspots that can generate nonselective cracking to reduce the value of theproduct hydrocarbons.

Improved apparatus and processes are sought in the mixing of carbonizedand regenerated catalyst.

SUMMARY OF THE INVENTION

We have found that the mixing chamber for process units that aredesigned to process large amounts of feed can become very large whichadds to the capital cost and requires more catalyst inventory to fillthe increased volume added by the chamber to an entire process unit.However, we have discovered that carbonized and regenerated catalyst canbe thoroughly mixed in the lower section of a reactor riser by use of achamber in a lower section of the riser.

In an apparatus embodiment, the present invention comprises an apparatusfor mixing two streams of catalyst comprising a riser. A first catalystconduit and a second catalyst conduit are in communication with theriser. A chamber in the riser is in communication with the firstcatalyst conduit. A wall of the chamber is spaced apart from a wall ofthe riser. Lastly, an opening is in the chamber. In an aspect, theopening is in a wall of the chamber.

In an additional apparatus embodiment, the present invention comprisesan apparatus for mixing two streams of catalyst comprising a riser. Afirst catalyst conduit and a second catalyst conduit are incommunication with the riser. A chamber in the riser is in communicationwith the first catalyst conduit and the second catalyst conduit. A wallof the chamber is spaced apart from a wall of the riser to provide anannular space. Lastly, an opening in the wall of the chamber is in theannular space.

In a further apparatus embodiment, the present invention comprises anapparatus for mixing two streams of catalyst comprising a riser. A firstcatalyst conduit and a second catalyst conduit are in communication withthe riser. A chamber in the riser is in communication with the firstcatalyst conduit and the second catalyst conduit. A wall of the chamberis spaced apart from a wall of the riser to provide an annular space.Lastly, an opening in the chamber is above a lowermost portion of aninlet of said second catalyst conduit into said riser.

In a process embodiment, the present invention comprises a process formixing two streams of catalyst comprising feeding a first stream ofcatalyst into a space between a wall of a riser and a wall of a chamberin the riser. A second stream of catalyst is fed to the riser. The firststream of catalyst is passed from the space into an opening in thechamber. Lastly, the first stream of catalyst and the second stream ofcatalyst are passed up the riser.

In an additional process embodiment, the present invention comprises aprocess for mixing two streams of catalyst comprising feeding a firststream of catalyst from a first catalyst conduit into a space between awall of a riser and a wall of a chamber in the riser. A second stream ofcatalyst is fed to the riser. The first stream of catalyst is passedfrom the space into an opening in the chamber. Lastly, the first streamof catalyst and the second stream of catalyst are passed up the riser.

In a further process embodiment, the present invention comprises aprocess for mixing two streams of catalyst comprising passing a firststream of catalyst from a first catalyst conduit into a chamber in theriser. A second stream of catalyst is fed from a second catalyst conduitinto a space between a wall of a riser and a wall of a chamber in theriser. The first stream of catalyst is passed from the chamber into thespace or the second stream of catalyst is passed from the space into thechamber through a plurality of openings in the chamber. Lastly, thefirst stream of catalyst and the second stream of catalyst are passed upthe riser.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, elevational view of an FCC unit incorporating thepresent invention.

FIG. 2 is a sectional view of FIG. 1 taken at segment 2-2.

FIG. 3 is a partial, schematic, elevational view of the FCC unit of FIG.1 incorporating an alternative embodiment of the present invention.

FIG. 4 is a schematic, elevational view of an alternative embodiment ofthe FCC unit of FIG. 1 incorporating an alternative embodiment of thepresent invention.

FIGS. 5 a, 5 b and 5 c are sectional views of FIG. 4 taken at segment5-5.

FIG. 6 is a partial, schematic, elevational view of the FCC unit of FIG.4 incorporating an alternative embodiment of the present invention.

FIG. 7 is a partial, schematic, elevational view of the FCC unit of FIG.4 incorporating an alternative embodiment of the present invention.

FIG. 8 is a sectional view of FIG. 7 taken at segment 8-8.

FIG. 9 is a partial, schematic, elevational view of the FCC unit of FIG.4 incorporating an alternative embodiment of the present invention.

FIG. 10 is a partial, schematic, elevational view of the FCC unit ofFIG. 4 incorporating an alternative embodiment of the present invention.

FIG. 11 is a sectional view of FIG. 10 taken at segment 11-11.

DEFINITIONS

The term “communication” means that material flow is operativelypermitted between enumerated components.

The term “downstream communication” means that at least a portion ofmaterial flowing to the subject in downstream communication mayoperatively flow from the object with which it communicates.

The term “upstream communication” means that at least a portion of thematerial flowing from the subject in upstream communication mayoperatively flow to the object with which it communicates.

The term “direct communication” means that flow from the upstreamcomponent enters the downstream component without passing through anintermediate vessel.

The term “feeding” means that the feed passes from a conduit or vesseldirectly to an object without passing through an intermediate vessel.

The term “passing” includes “feeding” and means that the material passesfrom a conduit or vessel to an object.

DETAILED DESCRIPTION OF THE INVENTION

The apparatus and process of the present invention is for mixingregenerated catalyst and carbonized catalyst for contact with ahydrocarbon feed. The present invention may be useful in any solids-gascontacting equipment. However, ready usefulness is found in an FCC unit.FIG. 1 shows an FCC unit 8 that includes a reactor vessel 20 and aregenerator vessel 50. A first regenerated catalyst conduit 12 transfersa first regenerated catalyst stream from the regenerator vessel 50 at arate regulated by a control valve 14 through a regenerated catalystinlet 15 of the first regenerated catalyst conduit 12 to the reactorriser 10. A second carbonized catalyst conduit 52 transfers a secondcarbonized catalyst stream from the reactor vessel 20 at a rateregulated by a control valve 53 through a carbonized catalyst inlet 97of the second carbonized catalyst conduit 52 to the reactor riser 10.

The riser 10 is an elongated vertical tube typically made of carbonsteel. The riser 10 may comprise an enlarged lower section 11 and anarrower upper section 17. The enlarged lower section 11 may have alarger diameter than the narrower upper section 17 of the riser. Theenlarged lower section 11 may include a hemispherical bottom. Theenlarged lower section 11 may include a frustoconical transition section13 that tapers between the enlarged diameter of the enlarged lowersection and the narrowed diameter of the upper section 17 of the riser.The first regenerated catalyst conduit 12 and a second carbonizedcatalyst conduit 52 may connect to the lower section 11 at a wall 90 ofthe lower section at inlets 15 and 97, respectively. In an aspect, oneor both of the first regenerated catalyst conduit and the secondcarbonized catalyst conduit do not extend into the riser 10 past thewall 90 of the enlarged lower section 11. The inner surface of theentire riser 10 may be coated with a refractory material.

A fluidization medium such as steam from a nozzle 16 and ring 19 in thelower section 11 urges catalyst upwardly through the riser 10 at arelatively high density. A plurality of feed distributors 18 in theupper section 17 of the riser 10 just above the transition section 13inject feed across the flowing stream of catalyst particles todistribute hydrocarbon feed to the riser 10. Upon contacting thehydrocarbon feed with catalyst in the reactor riser 10 the heavierhydrocarbon feed cracks to produce lighter gaseous hydrocarbon productwhile coke is deposited on the catalyst particles to produce carbonizedcatalyst.

A conventional FCC feedstock and higher boiling hydrocarbon feedstockare suitable feeds. The most common of such conventional feedstocks is a“vacuum gas oil” (VGO), which is typically a hydrocarbon material havinga boiling range of from 343° to 552° C. (650 to 1025° F.) prepared byvacuum fractionation of atmospheric residue. Such a fraction isgenerally low in coke precursors and heavy metal contamination which canserve to contaminate catalyst. Heavy hydrocarbon feedstocks to whichthis invention may be applied include heavy bottoms from crude oil,heavy bitumen crude oil, shale oil, tar sand extract, deasphaltedresidue, products from coal liquefaction, atmospheric and vacuum reducedcrudes. Heavy feedstocks for this invention also include mixtures of theabove hydrocarbons and the foregoing list is not comprehensive. It isalso contemplated that lighter recycle or previously cracked feeds suchas naphtha may be a suitable feedstock.

The reactor vessel 20 is in downstream communication with the riser 10.In the reactor vessel, the carbonized catalyst and the gaseous productare separated. The resulting mixture of gaseous product hydrocarbons andcarbonized catalyst continues upwardly through the riser 10 into thereactor vessel 20 in which the carbonized catalyst and gaseous productare separated. A pair of disengaging arms 22 may tangentially andhorizontally discharge the mixture of gas and catalyst from a top of theriser 10 through one or more outlet ports 24 (only one is shown) into adisengaging vessel 26 to effect partial separation of gases from thecatalyst. Two, three or four disengaging arms 22 may be used dependingon the size of the FCC unit.

A transport conduit 28 carries the hydrocarbon vapors, includingstripped hydrocarbons, stripping media and entrained catalyst to one ormore cyclones 30 in the reactor vessel 20 which separates carbonizedcatalyst from the hydrocarbon gaseous stream. The disengaging vessel 26is partially disposed in the reactor vessel 20 and can be consideredpart of the reactor vessel 20. A collection plenum 34 in the reactorvessel 20 gathers the separated hydrocarbon gaseous streams from thecyclones 30 for passage to an outlet nozzle 36 and eventually into afractionation recovery zone (not shown). Diplegs 38 discharge catalystfrom the cyclones 30 into a lower bed 29 in the reactor vessel 20. Thecatalyst with adsorbed or entrained hydrocarbons may eventually passfrom the lower bed 29 into an optional stripping section 40 across ports42 defined in a wall of the disengaging vessel 26. Catalyst separated inthe disengaging vessel 26 may pass directly into the optional strippingsection 40 via a bed 41. A fluidizing conduit 45 delivers inertfluidizing gas, typically steam, to the stripping section 40 through afluidizing distributor 46. The stripping section 40 contains baffles 43,44 or other equipment to promote contacting between a stripping gas andthe catalyst. The stripped carbonized catalyst leaves the strippingsection 40 of the disengaging vessel 26 of the reactor vessel 20 with alower concentration of entrained or adsorbed hydrocarbons than it hadwhen it entered or if it had not been subjected to stripping. A firstportion of the carbonized catalyst leaves the disengaging vessel 26 ofthe reactor vessel 20 through a spent catalyst conduit 48 and feeds intothe regenerator vessel 50 at a rate regulated by a control valve 51. Asecond portion of the carbonized catalyst that has been coked in thereactor riser 10 leaves the disengaging vessel 26 of the reactor vessel20 and is fed through the second carbonized catalyst conduit 52 back tothe riser 10 at a rate regulated by a control valve 53. The secondcarbonized catalyst conduit 52 is in downstream communication with thereactor vessel 20. The second carbonized catalyst conduit 52 is indownstream communication with the outlet port 24 of the riser 10 and inupstream communication with a carbonized catalyst inlet 97 of the secondcarbonized catalyst conduit 52 to the riser 10.

The riser 10 of the FCC process is maintained at high temperatureconditions which generally include a temperature above about 425° C.(797° F.). In an embodiment, the reaction zone is maintained at crackingconditions which include a temperature of from about 480° to about 621°C. (896° to 1150° F.) at the riser outlet port 24 and a pressure fromabout 69 to about 517 kPa (ga) (10 to 75 psig) but typically less thanabout 275 kPa (ga) (40 psig). The catalyst-to-oil ratio, based on theweight of catalyst and feed hydrocarbons entering the bottom of theriser, may range up to 30:1 but is typically between about 4:1 and about10:1 and may range between 7:1 and 25:1. Hydrogen is not normally addedto the riser, although hydrogen addition is known in the art. Steam maybe passed into the riser 10 and reactor vessel 20 equivalent to about2-35 wt-% of feed. Typically, however, the steam rate will be betweenabout 2 and about 7 wt-% for maximum gasoline production and about 10 toabout 20 wt-% for maximum light olefin production. The average residencetime of catalyst in the riser may be less than about 5 seconds. The typeof catalyst employed in the process may be chosen from a variety ofcommercially available catalysts. A catalyst comprising a zeoliticmaterial such as Y Zeolite is preferred, but the older style amorphouscatalysts can be used if desired. Additionally, shape-selectiveadditives such as ZSM-5 may be included in the catalyst composition toincrease light olefin production.

The regenerator vessel 50 is in downstream communication with thereactor vessel 20. In the regenerator vessel 50, coke is combusted fromthe portion of carbonized catalyst delivered to the regenerator vessel50 by contact with an oxygen-containing gas such as air to provideregenerated catalyst. The regenerator vessel 50 may be a combustor typeof regenerator, which may use hybrid turbulent bed-fast fluidizedconditions in a high-efficiency regenerator vessel 50 for completelyregenerating carbonized catalyst. However, other regenerator vessels andother flow conditions may be suitable for the present invention. Thespent catalyst conduit 48 feeds carbonized catalyst to a first or lowerchamber 54 defined by outer wall 56 through a spent catalyst inlet chute62. The carbonized catalyst from the reactor vessel 20 usually containscarbon in an amount of from 0.2 to 2 wt-%, which is present in the formof coke. Although coke is primarily composed of carbon, it may containfrom 3 to 12 wt-% hydrogen as well as sulfur and other materials. Anoxygen-containing combustion gas, typically air, enters the lowerchamber 54 of the regenerator vessel 50 through a conduit 64 and isdistributed by a distributor 66. As the combustion gas enters the lowerchamber 54, it contacts carbonized catalyst entering from chute 62 andlifts the catalyst at a superficial velocity of combustion gas in thelower chamber 54 of perhaps at least 1.1 m/s (3.5 ft/s). In anembodiment, the lower chamber 54 may have a catalyst density of from 48to 320 kg/m³ (3 to 20 lb/ft³) and a superficial gas velocity of 1.1 to6.1 m/s (3.5 to 20 ft/s). The oxygen in the combustion gas contacts thecarbonized catalyst and combusts carbonaceous deposits from the catalystto at least partially regenerate the catalyst and generate flue gas.

In an embodiment, to accelerate combustion of the coke in the lowerchamber 54, hot regenerated catalyst from a dense catalyst bed 59 in anupper or second chamber 70 may be recirculated into the lower chamber 54via an external recycle catalyst conduit 67 regulated by a control valve69. Hot regenerated catalyst enters the lower chamber 54 through aninlet chute 63. Recirculation of regenerated catalyst, by mixing hotcatalyst from the dense catalyst bed 59 with relatively coolercarbonized catalyst from the spent catalyst conduit 48 entering thelower chamber 54, raises the overall temperature of the catalyst and gasmixture in the lower chamber 54.

The mixture of catalyst and combustion gas in the lower chamber 54ascend through a frustoconical transition section 57 to the transport,riser section 60 of the lower chamber 54. The riser section 60 defines atube which is preferably cylindrical and extends preferably upwardlyfrom the lower chamber 54. The mixture of catalyst and gas travels at ahigher superficial gas velocity than in the lower chamber 54. Theincreased gas velocity is due to the reduced cross-sectional area of theriser section 60 relative to the cross-sectional area of the lowerchamber 54 below the transition section 57. Hence, the superficial gasvelocity may usually exceed about 2.2 m/s (7 ft/s). The riser section 60may have a lower catalyst density of less than about 80 kg/m³ (5lb/ft³).

The regenerator vessel 50 also includes an upper or second chamber 70.The mixture of catalyst particles and flue gas is discharged from anupper portion of the riser section 60 into the upper chamber 70.Substantially completely regenerated catalyst may exit the top of thetransport, riser section 60, but arrangements in which partiallyregenerated catalyst exits from the lower chamber 54 are alsocontemplated. Discharge is effected through a disengaging device 72 thatseparates a majority of the regenerated catalyst from the flue gas. Inan embodiment, catalyst and gas flowing up the riser section 60 impact atop elliptical cap 65 of the riser section 60 and reverse flow. Thecatalyst and gas then exit through downwardly directed discharge outlets73 of disengaging device 72. The sudden loss of momentum and downwardflow reversal cause a majority of the heavier catalyst to fall to thedense catalyst bed 59 and the lighter flue gas and a minor portion ofthe catalyst still entrained therein to ascend upwardly in the upperchamber 70. Cyclones 82, 84 further separate catalyst from ascending gasand deposits catalyst through dip legs 85, 86 into dense catalyst bed59. Flue gas exits the cyclones 82, 84 and collects in a plenum 88 forpassage to an outlet nozzle 89 of regenerator vessel 50 and perhaps intoa flue gas or power recovery system (not shown). Catalyst densities inthe dense catalyst bed 59 are typically kept within a range of fromabout 640 to about 960 kg/m³ (40 to 60 lb/ft³). A fluidizing conduit 74delivers fluidizing gas, typically air, to the dense catalyst bed 59through a fluidizing distributor 76. In a combustor-style regenerator,approximately no more than 2% of the total gas requirements within theprocess enter the dense catalyst bed 59 through the fluidizingdistributor 76. In this embodiment, gas is added here not for combustionpurposes but only for fluidizing purposes, so the catalyst will fluidlyexit through the catalyst conduits 67 and 12. The fluidizing gas addedthrough the fluidizing distributor 76 may be combustion gas. In the casewhere partial combustion is effected in the lower chamber 54, greateramounts of combustion gas will be fed to the upper chamber 70 throughfluidizing conduit 74.

From about 10 to 30 wt-% of the catalyst discharged from the lowerchamber 54 is present in the gases above the outlets 73 from the risersection 60 and enter the cyclones 82, 84. The regenerator vessel 50 maytypically require 14 kg of air per kg of coke removed to obtain completeregeneration. When more catalyst is regenerated, greater amounts of feedmay be processed in a conventional reactor riser. The regenerator vessel50 typically has a temperature of about 594 to about 732° C. (1100 to1350° F.) in the lower chamber 54 and about 649 to about 760° C. (1200to 1400° F.) in the upper chamber 70. The regenerated catalyst conduit12 is in downstream communication with the regenerator vessel 50 andcommunicates with the riser 10. Regenerated catalyst from dense catalystbed 59 is transported through regenerated catalyst conduit 12 as a firststream of catalyst from the regenerator vessel 50 back to the reactorriser 10 through the control valve 14 where it again contacts feed asthe FCC process continues. The carbonized catalyst in conduit 52comprises a second stream of catalyst.

The first stream of regenerated catalyst and a second stream ofcarbonized catalyst fed into the riser 10 tend not to mix thoroughlybefore contacting the hydrocarbon feed. Accordingly, the feed canencounter catalyst at varying temperatures resulting in non-selectivecracking to a composition with relatively more undesirable products. Inan aspect, to ensure mixing between the carbonized catalyst and theregenerated catalyst, means is necessary in the lower end 11 of theriser 10 to facilitate catalyst mixing.

In an embodiment shown in FIG. 1, the first regenerated catalyst conduit12 and the second carbonized catalyst conduit 52 connect to and are incommunication with the riser 10. The first stream of regeneratedcatalyst in the first regenerated catalyst conduit 12 and the secondstream of carbonized catalyst in the second carbonized catalyst conduit52 are fed to the riser 10 and mixed together. One or both of the firstregenerated catalyst conduit 12 and the second carbonized catalystconduit 52 may tangentially connect to the enlarged lower section 11 ofthe riser 10 tangentially to impart an angular motion to catalystdischarged into the riser to promote mixing therein. Additionally, rampsmay be installed at the connection between one or both of the firstregenerated catalyst conduit 12 and the second carbonized catalystconduit 52 and the enlarged lower section 11 of the riser 10 also topromote mixing in the enlarged lower section 11. After mixing, a mixtureof the first stream of regenerated catalyst and the second stream ofcarbonized catalyst pass upwardly in the riser 10.

The riser may include a chamber 92. In an aspect, the enlarged lowersection 11 of the riser 10 may include the chamber 92. In an aspect, thechamber 92 is contained in the enlarged lower section 11 of the riser.The chamber 92 in the riser 10 may be in downstream communication withthe first catalyst conduit 12. The chamber 92 in the riser 10 may alsobe in downstream communication with the second catalyst conduit 52. Thechamber 92 may have an outer wall 94 that is spaced apart from an innersurface of the wall 90 of the enlarged lower section 11 of the riser 10.In an aspect, the chamber 92 is radially centered in the enlarged lowersection 11 of the riser 10. In other words, although not shown, thechamber 92 has a central longitudinal axis aligned with a centrallongitudinal axis of the riser. In a further aspect, the outer wall 94of the chamber is a vertical wall.

The wall 94 of the chamber 92 and the wall 90 of the riser define aspace 96 therebetween. In an aspect, chamber 92 and the enlarged lowersection 11 may each comprise a cylinder that together they define anannular space 96 between the wall 94 of the chamber 92 and the wall 90of the enlarged lower section 11. The first regenerated catalyst conduit12 and the second carbonized catalyst conduit 52 may communicate withthe space 96, so the first regenerated catalyst conduit 12 feeds thefirst stream of regenerated catalyst to the space 96 and the secondcarbonized catalyst conduit 52 feeds the second stream of carbonizedcatalyst to the space 96. The catalyst in the space 96 is fluidized byfluidizing gas from fluidizing distributor 19.

The chamber 92 may include at least one opening 98 in the wall 94located in the space 96. The opening 98 may be spaced apart from thewall 90 of the riser 10. The opening 98 may serve as an entrance to aninterior of the chamber 92. The chamber 92 may be in communication withthe first regenerated catalyst conduit 12 and the second carbonizedcatalyst conduit 52, so at least a portion of the first stream ofregenerated catalyst and at least a portion of the second stream ofcarbonized catalyst may pass from the space 96 into the chamber 92through the opening 98 in the chamber. In an aspect, an upper mostportion of the opening 98 may be at an elevation above a lower mostportion, and preferably an upper most portion, of the inlet 97. In afurther aspect, an upper most portion of the opening 98 may be at anelevation above a lower most, and preferably an upper most portion, ofthe inlet 15. Hence, the first stream of regenerated catalyst may passupwardly from the inlet 15 of the first catalyst conduit 12, and thesecond stream of carbonized catalyst may pass upwardly from the inlet 97of the second catalyst conduit 52 through the opening 98 into thechamber 92 through the space 96 between the wall 90 of the riser 10 andthe wall 94 of the chamber 92.

In an aspect, the at least one opening 98 in the wall 94 of the chambermay serve as an exit from the chamber 92. Consequently, the first streamof regenerated catalyst and the second stream of carbonized catalyst maypass through the opening 98 from the chamber 92 into the space 96. Byvirtue of the first and second catalyst streams entering into andexiting from the chamber 92 through the at least one opening 98 in thewall 94 of the chamber 92, the catalyst streams mix together to providea mixed stream of catalyst with a more-homogeneous temperaturethroughout the mixed stream of catalyst. The first and second catalyststreams pass from the chamber into the riser and pass upwardly from theenlarged lower section 11 and are contacted with feed from feeddistributors 18 in the upper section 17 of the riser 10.

One or a plurality of openings 98 may be provided in the wall 94. Atleast one opening 98 may have an elongated configuration that is spacedfrom the top of the chamber 92.

FIG. 2 shows a plan sectional view of segment 2-2 taken in FIG. 1.Refractory lining 104 on the wall 94 of the chamber 92 and the walls ofthe lower section 11 of the riser, the first regenerated catalystconduit 12 and the second carbonized catalyst conduit 52 are shown inFIG. 2, but not in FIG. 1. The wall 94 of the chamber 92 comprises threearcuate sections 94 a-c that define three openings 98 a-c. Two openings98 a and 98 b may have a smaller width than a third opening 98 c. In anaspect, the two smaller openings 98 a and 98 b have the same arcuatewidth. Arcuate section 94 a opposes the nearest catalyst conduit whichis the first regenerated catalyst conduit 12 and particularly the inlet15 thereof. Arcuate section 94 b also opposes the nearest catalystconduit which is the second carbonized catalyst conduit 52 andparticularly the inlet 97 thereof. The third arcuate section 94 c isoptional. Dashed lines show central longitudinal axis A of the firstregenerated catalyst conduit into the riser 10 and central longitudinalaxis B of the second carbonized catalyst conduit 52 into the riser. Theopenings 98 are all radially unaligned with a longitudinal axis A, B ofa nearest one of the first regenerated catalyst conduit 12 and thesecond carbonized catalyst conduit 52 into the riser. In other words,the first regenerated catalyst conduit 12 and the second carbonizedcatalyst conduit 52 are azimuthal to openings 98 a-c. Arcuate sections94 a and 94 b may be narrower or wider than the inlet 15, 97 of aclosest catalyst conduit 12, 52 into the riser 10.

As the first stream of regenerated catalyst enters into the space 96from the regenerated catalyst conduit 12, it encounters arcuate section94 a and passes along arcuate section 94 a of the wall 94 of the chamber92 before the first stream of catalyst enters into an opening 98 a, 98 cor perhaps 98 b after passing along arcuate section 94 c or 94 b. As thesecond stream of carbonized catalyst enters into the space 96 from thesecond carbonized catalyst conduit 52, it encounters arcuate section 94b and passes along arcuate section 94 b of the wall of the chamber 92before the second stream of catalyst enters into an opening 98 b, 98 cor perhaps 98 a after passing along arcuate section 94 a or 94 c. Thefirst stream of catalyst and the second stream of catalyst mix togetherinside of the chamber 92 and the first stream of catalyst and the secondstream of catalyst exit the chamber 92 through the openings 98 a-c in amixed catalyst stream. The first stream of catalyst and the secondstream of catalyst mix together in the space 96 and mix together in thechamber 92 to provide a mixture of catalyst in a mixed catalyst stream.

Turning back to FIG. 1, the chamber 92 has a closed top 102 which maycomprise a hemispherical head that prevents catalyst from exitingupwardly through the top of the chamber 92 in alignment with the riser10. The closed top 102 is disposed at an elevation about as high as thetop of the enlarged lower section 11. The closed top 102 serves toreduce the cross sectional area of the enlarged lower section 11 toabout half of the cross sectional area of the enlarged lower section 11below the closed top 102 which includes the interior of the chamber 92.Consequently, the superficial velocity in the enlarged lower section 11at the closed top is about twice the superficial velocity below the topin the enlarged cross sectional area. At least one, and preferably theplurality of openings 98 in the chamber 92 are spaced from the top 102.In an aspect, the openings 98 are spaced from a bottom 106 of thehemispherical head of the top 102 by a space that is at least a quarterof the diameter “D” of the chamber 92. The top 102 demarks an upperboundary between the chamber 92 and the riser 10.

It is anticipated that the chamber 92 be made of stainless steel such as300 Series stainless steel and be lined with refractory. The edges ofthe openings 98 in the wall 94 may have a construction that preventserosion. For example, the edges may be thicker than the rest of the wall94. The edges may also be curved to deflect potentially eroding catalystparticles. Moreover, a weld bead may be welded to the edges to alsoresist erosion of the edges. Additionally, the chamber 92 may be made ofor coated with a ceramic or other material that resists erosion.

FIG. 3 illustrates a further embodiment of FIG. 1 with a differentmixing chamber 392. Elements in FIG. 3 with the same configuration as inFIG. 1 will have the same reference numeral as in FIG. 1. Elements inFIG. 3 which have a different configuration as the corresponding elementin FIG. 1 will have the same reference numeral but be preceded with thedigit “3”. Everything in FIG. 3 is the same as in FIG. 1 except themixing chamber 392.

In FIG. 3, the chamber 392 is disposed in an enlarged lower section 11of the riser 10. The first regenerated catalyst conduit 12 and thesecond carbonized catalyst conduit 52 deliver catalyst to a space 396 inthe enlarged lower section 11 of the riser 10.

The chamber 392 in the riser 10 may communicate with the firstregenerated catalyst conduit 12 and the second catalyst conduit 52. Thechamber 392 may have an outer wall 394 that is spaced apart from aninner surface of the 90 wall of the enlarged lower section 11 of theriser 10. In an aspect, the chamber 392 is radially centered in theenlarged lower section 11 of the riser 10. The wall 394 of the chamber392 and the wall 90 of the riser define a space 396 therebetween. In anaspect, the chamber 392 may comprise a cylindrical chamber 392 thatdefines an annular space 396 between the wall 394 of the chamber 392 andthe wall 90 of the enlarged lower section 11. The first regeneratedcatalyst conduit 12 and the second carbonized catalyst conduit 52 maycommunicate with the space 396, so the first regenerated catalystconduit 12 feeds the first stream of regenerated catalyst to the space396 and the second carbonized catalyst conduit 52 feeds the secondstream of carbonized catalyst to the space 396.

The chamber 392 includes an opening 398 in the wall 394 located in thespace 396. The opening 398 serves as an entrance to and an exit from aninterior of the chamber 392. Unlike in FIGS. 1 and 2, the opening 398may be in alignment with the first catalyst conduit 12. Although thefirst regenerated catalyst conduit 12 is not connected to the chamber392 through the opening 398, the first regenerated catalyst conduit hasa longitudinal axis C that intersects the opening 398. The trajectory offirst stream of regenerated catalyst exits the first regeneratedcatalyst conduit and is directed into the chamber 392 through theopening 398 in a manner that would be considered feeding even though thefirst regenerated catalyst conduit 12 and the chamber 392 are notconnected. The chamber 392 may be in communication with the firstregenerated catalyst conduit 12 and the second carbonized catalystconduit 52, so at least a portion of the first stream of regeneratedcatalyst that misses the opening 398 and enters the space 396 and thesecond stream of carbonized catalyst may pass from the space 396 intothe chamber 392 through the opening 398 in the chamber. The secondcarbonized catalyst conduit may not be in alignment with the opening398, so the second stream of carbonized catalyst is not directed intothe opening 398, but travels along the wall 394 and passes into opening398 indirectly. It is contemplated that the second carbonized catalystconduit 52 could be aligned with an additional opening in the wall 394in an unshown embodiment.

The first stream of regenerated catalyst and the second stream ofcatalyst may pass from the chamber 392 back into the space 396 throughthe opening 398. By virtue of the first and second catalyst streamsentering into and exiting the chamber through the opening 398 in thewall 394 of the chamber 392, the catalyst streams mix together toprovide a mixed stream of catalyst with a more-homogeneous temperaturethroughout the mixed stream of catalyst.

The chamber 392 may have at least one additional exit opening 110. Theat least one additional exit opening 110 may be in the vertical wall 394and provide an inlet to an end of a tubular swirl arm 112 that has anoutlet opening 114 at an opposite end of the swirl arm 112. The swirlarm 112 has a swirl-imparting configuration. The swirl-impartingconfiguration may be an arcuate tube that has a rectangular crosssection. The chamber 394 may have at least two swirl arms 112 each witha respective exit opening 110. Two are shown in FIG. 3 with one opening110 in phantom. Four swirl arms 112 are envisioned. The opening 398 inthe wall 394 of the chamber 392 in upstream communication with the exitopenings 110 and the swirl arms 112. The exit opening 110 may have alower most portion that is disposed at an elevation above a lowermostportion, and preferably an upper most portion of the opening 398.Consequently, the catalyst entering the chamber 394 through the opening398 travels upwardly to the exit opening 110. Fluidization gas from thedistributor 16 propels catalyst entering the chamber 392 upwardly to theexit openings 110 and concomitant swirl arms 112. As the mixed stream ofcatalyst passes from the chamber 394 into the swirl arms 112, thearcuate configuration imparts a swirling motion to the mixed catalyststream. The exit opening 110 and the swirl arm 112 may be configuredtangentially to generate a swirling motion in the space 396 while themixed stream of catalyst passes from the chamber 394 into the space 396.The swirling motion in the space serves to increase mixing in the space396 and in the chamber 392. The first and second catalyst streams passfrom the chamber into the riser and pass upwardly from the enlargedlower section 11 and are contacted with feed from feed distributors.Because the first regenerated catalyst conduit 12 is aligned with theopening 398, it is expected that most of the catalyst entering thechamber 392 will exit through the openings 110.

FIG. 4 illustrates an alternative embodiment in which the firstregenerated catalyst stream from the first regenerated catalyst conduit12 is fed into the chamber 492. In an aspect, the chamber 492 is indownstream communication only with the first regenerated catalystconduit 412, and only the first stream of regenerated catalyst fromconduit 412 is fed to the chamber 492. Elements in FIG. 4 with the sameconfiguration as in FIG. 1 will have the same reference numeral as inFIG. 1. Elements in FIG. 4 which have a different configuration as thecorresponding element in FIG. 1 will have the same reference numeral butbe preceded with the digit “4” instead of digit “1”.

In an embodiment shown in FIG. 4, an FCC unit 408 has a firstregenerated catalyst conduit 412 and a second carbonized catalystconduit 452 that are in upstream communication with a riser 410. Thesecond carbonized catalyst conduit 452 connects to a riser 410 at aninlet 497. The riser 410 may comprise an enlarged lower section 411, atransition section 13 and a narrower upper section 17 as in FIG. 1.Fluidizing gas from a distributor 419 fluidizes catalyst in the lowersection 411. The riser 410 is in downstream communication with the firstcatalyst conduit 412. The first regenerated catalyst conduit 412 feedsthe first regenerated catalyst stream to a chamber 492 which extendsinto the enlarged lower section 411 of the riser 410. At least a portionof the chamber 492 is contained in the riser 410 and, in an aspect, inthe enlarged lower section 411 of the riser 410. In an aspect, thechamber 492 in the riser 410 may be in downstream communication with thefirst regenerated catalyst conduit 412. The first regenerated catalystconduit 412 may feed regenerated catalyst to the chamber 492 at an inlet415 of the first regenerated catalyst conduit 412 to the chamber 492.The chamber 492 may include a sub-riser 120 that is connected to thefirst regenerated catalyst conduit 412. Consequently, the firstregenerated catalyst conduit 412 feeds the first stream of regeneratedcatalyst into the chamber 492 at the sub-riser. Fluidizing gas from adistributor 416 in the sub-riser 120 fluidizes the first regeneratedcatalyst stream in the chamber 492 and lifts it upwardly in the chamber492.

The second catalyst conduit 452 is in upstream communication with theriser 410. The second catalyst conduit 452 may connect to the lowersection 411 of the riser 410 at a wall 490 of the lower section 411. Inan aspect, the second catalyst conduit does not extend into the riser410 past the wall 490 of the enlarged lower section 411. The chamber 492may have an outer wall 494 that is spaced apart from an inner surface ofthe wall 490 of the enlarged lower section 411 of the riser 410. In anaspect, the chamber 492 is radially centered in the enlarged lowersection 411 of the riser 410. In other words, although not shown, thechamber 492 has a central longitudinal axis aligned with a centrallongitudinal axis of the riser. In a further aspect, the outer wall 494of the chamber 492 is a vertical wall.

The wall 494 of the chamber 492 and the wall 490 of the enlarged section411 of the riser 410 are spaced apart to define a space 496. In anaspect, the enlarged lower section 411 may be cylindrical and thechamber 492 may comprise a cylindrical chamber 492 that define anannular space 496 between the wall 494 of the chamber 492 and the wall490 of the enlarged lower section 411. The second carbonized catalystconduit 452 may communicate with the space 496. The second carbonizedcatalyst conduit 452 feeds the second stream of carbonized catalyst tothe riser 410 and in an aspect to the space 496 in the enlarged lowersection 411 of the riser 410.

The first stream of catalyst may be passed from the chamber 492 into thespace 496. The chamber 492 may have at least one exit opening 498. Theopening 498 may be spaced apart from the wall 490 of the riser 410. Theexit opening 498 may be in the vertical wall 494 of the chamber 492. Inan aspect, upper most portions of openings 498 may be at an elevationabove a lower most portion, and preferably an upper most portion, of theinlet 415. Hence, the first stream of regenerated catalyst may passupwardly from the inlet 415 of the first catalyst conduit 412 into thechamber 492 to the openings 498.

The first catalyst stream may pass from the opening 498 in the chamber492 into the riser 10 and mixes with the second carbonized catalyststream. In an aspect, the first catalyst stream passes from an opening498 in the chamber 492 into the enlarged lower section 411 of the riser410 in and mixes with the second carbonized catalyst stream fed to theenlarged lower section 411 by the carbonized catalyst conduit 452. In anaspect, the first regenerated catalyst stream and the second carbonizedcatalyst stream mix in the space 496. The mixture of the firstregenerated catalyst stream and the second carbonized catalyst streampass upwardly into the riser from the enlarged lower section 411 and arecontacted with feed from feed distributors 18. Because the regeneratedcatalyst stream will be exiting the openings 498 propelled by fluidizinggas from distributor 416 very little if any of the second carbonizedcatalyst will enter the chamber 492 through the opening 498.Consequently, the second carbonized catalyst conduit 452 is out ofcommunication with the chamber 492, and the second carbonized catalyststream is not passed into the chamber 492. The chamber 492 has a top 402to prevent the first regenerated catalyst stream from exiting thechamber 492 upwardly in alignment with the riser 410. The top 402demarks an upper boundary between the chamber 492 and the riser 10.

FIG. 5 a shows a plan sectional view of segment 5-5 taken in FIG. 4.FIG. 5 a shows the first regenerated catalyst conduit 412 and the secondcarbonized catalyst conduit 452 in upstream communication with the lowersection 411 of the riser 410. Openings 498 constitute windows in thechamber 492.

FIG. 5 b shows an alternative plan sectional view of segment 5-5 takenin FIG. 4 in which each opening 498 b is on an inlet end of a stub tube122 that may have a rectangular or other cross section. The stub tubehas an opening 124 on an outlet end that provides communication betweenan interior of the chamber 492 and the space 496.

FIG. 5 c shows another, alternative plan sectional view of segment 5-5taken in FIG. 4 in which each opening 498 c is an inlet at an end of aswirl tube 126 that may have a rectangular cross section. The swirl tubehas an open outlet end 128 that provides communication between aninterior of the chamber 492 and the space 496. The swirl-impartingconfiguration may be an arcuate tube. An opening in a wall 494 of thechamber 492 is in upstream communication with the swirl arm 124. As thefirst stream of regenerated catalyst passes from the chamber 492 intothe swirl arm 124 the arcuate configuration imparts a swirling motion tothe first catalyst stream while it passes from the chamber 494 into thespace 496 through openings 498 c. The swirling motion in the spaceserves to increase mixing of the first stream of regenerated catalystand the second stream of carbonized catalyst in the space 496. Thechamber 494 may have at least two swirl arms 124 each with a respectiveexit opening 498 c. Four swirl arms 124 are shown in FIG. 5 c each withrespective exit openings 498 c.

FIG. 6 illustrates an alternative embodiment of FIG. 4 in which achamber 692 has an open top. In this embodiment, the first regeneratedcatalyst stream from the first regenerated catalyst conduit 412 is fedinto the chamber 692 at an inlet 415 of the first regenerated catalystconduit 412 to the chamber 692. The chamber 692 is in downstreamcommunication only with the first regenerated catalyst conduit 412, notthe second carbonized catalyst conduit 452.

Elements in FIG. 6 with the same configuration as in FIG. 4 will havethe same reference numeral as in FIG. 4. Elements in FIG. 6 which have adifferent configuration as the corresponding element in FIG. 4 will havethe same reference numeral but be preceded with the digit “6” which willreplace the digit “4” in most cases.

The embodiment of FIG. 6 has generally the same configuration as theembodiment of FIG. 4. The first regenerated catalyst conduit 412 feedscatalyst to the chamber 692 and the second carbonized catalyst conduit452 feeds catalyst to a space 696. The chamber 692 has a frustoconicalwall 694 above the sub-riser 120 to provide a venturi device. The firststream of regenerated catalyst propelled upwardly by fluidizing gas fromdistributor 416 is accelerated as it exits an opening 698 from thechamber 692 because the opening 698 is narrowed due to the graduallydecreasing inner diameter ascending in the chamber 692. The acceleratedfirst stream of regenerated catalyst provides an eductor effect toimprove mixing with the second stream of carbonized catalyst entrainedupwardly in the space 696 by fluidizing gas from distributor 419 and bythe eductor effect of the first stream of regenerated catalyst exitingthe opening 698 under acceleration. The mixed stream of catalyst travelsupwardly in the riser 410 to be contacted with feed. In an aspect,opening 698 may be at an elevation above a lower most portion, andpreferably an upper most portion, of the inlet 415. Hence, the firststream of regenerated catalyst may pass upwardly from the inlet 415 ofthe first catalyst conduit 412 into the chamber 692 to the opening 698.The opening 698 demarks an upper boundary between the chamber 692 andthe riser 410.

FIGS. 7 and 8 illustrate an alternative embodiment of FIG. 4 in whichthe chamber 792 also has an open top. FIG. 8 is a plan sectional view ofsegment 8-8 taken in FIG. 7. In this embodiment, the first regeneratedcatalyst stream from the first regenerated catalyst conduit 412 is fedinto a chamber 792 which is in downstream communication only with thefirst regenerated catalyst conduit 412, not a second carbonized catalystconduit 752. Elements in FIG. 7 with the same configuration as in FIG. 4will have the same reference numeral as in FIG. 4. Elements in FIG. 7which have a different configuration as the corresponding element inFIG. 4 will have the same reference numeral but be preceded with thedigit “7” which will replace the digit “4” in most cases.

The embodiment of FIG. 7 has a generally similar configuration as theembodiment of FIG. 4. A riser 710 in FIG. 7 is not shown to have anenlarged lower section 411 but it may. The first regenerated catalystconduit 412 feeds catalyst to the chamber 792 and a second carbonizedcatalyst conduit 752 feeds catalyst to a space 796. The chamber isfluidized by fluidizing gas from a distributor 716 and the riser 710 isfluidized by fluidizing gas from distributor 719.

It can be seen in FIG. 8 that the second carbonized catalyst conduit 752may be tangentially arranged with respect to the riser so as to give thecarbonized catalyst a angular component upon entering the riser 710.Swirl vanes 130 are arranged in the space 796 to further impart angularmomentum to the carbonized catalyst in agreement with the tangentialarrangement of the second carbonized catalyst conduit 752. Arrow “E”shows the angular direction in which catalyst is induced to swirl byswirl vanes 130 and the tangentially connected second carbonizedcatalyst conduit 752. The first regenerated catalyst conduit 412 isradially arranged with respect to the sub-riser 120 of the chamber 792.

The chamber 792 has an opening 798 at its top, so the first regeneratedcatalyst stream may exit the opening upwardly in alignment with theriser 710. The space 796 includes swirl vanes 130 between the wall 790of the riser 710 and the wall 794 of the chamber 792 adjacent to theopening 798. The top of the chamber 792 is shown in phantom because itis hidden behind the vanes 130. A plurality of swirl vanes 130 may beinstalled each having a helical configuration to impart angular momentumto catalyst exiting therethrough. The swirl vanes 130 may have an upperend that extends above the opening 798 at the top of the chamber 792. Asthe second stream of carbonized catalyst ascends from the space 796 tothe riser 710 above the chamber 792 pushed upwardly therethrough byfluidizing gas from distributor 719, the swirl vanes 130 impart furtherangular momentum to the carbonized catalyst. The second stream ofcarbonized catalyst may flow through the vanes at a velocity in therange of about 1 m/s (3 ft/s) to about 9.2 m/s (30 ft/s) and flux inrange of about 244 kg/m²/s (50 lb/ft²/s) to 1464 kg/m²/s (300lb/ft2/sec). The high flux, swirling second stream of carbonizedcatalyst mixes with the first stream of regenerated catalyst exiting thechamber 792 through opening 798 propelled by fluidizing gas from thedistributor 716. The mixed stream of catalyst travels upwardly in theriser 710 to be contacted with hydrocarbon feed. In an aspect, theopening 798 may be at an elevation above a lower most portion, andpreferably an upper most portion, of the inlet 415. Hence, the firststream of regenerated catalyst may pass upwardly from the inlet 415 ofthe first catalyst conduit 412 into the chamber 492 to the opening 798.The opening 798 demarks an upper boundary between the chamber 792 andthe riser 710.

FIG. 9 illustrates an alternative embodiment of FIG. 4 in which thechamber 492 has an open top and the second stream of carbonized catalystenters into the chamber. Elements in FIG. 9 with the same configurationas in FIG. 4 will have the same reference numeral as in FIG. 4. Elementsin FIG. 9 which have a different configuration as the correspondingelement in FIG. 4 will have the same reference numeral but be precededwith the digit “9” instead of the digit “4” in most cases.

The embodiment of FIG. 9 has a similar configuration as the embodimentof FIG. 4. The first regenerated catalyst conduit 412 feeds catalyst toa chamber 992 at inlet 415 and the second carbonized catalyst conduit452 feeds catalyst to a space 996 in enlarged lower section 911 of theriser 910 at inlet 497. The first regenerated catalyst stream from thefirst regenerated catalyst conduit 412 is fed into the chamber 992 whichis in downstream communication only with the first regenerated catalystconduit 412. The chamber 992 may extend upwardly through an entireenlarged lower section 911. However, a baffle 132 may prevent catalystfrom ascending in the space 996 adjacent to the frustoconical transitionsection 913 of the riser 910. Openings 998 in a wall 994 of the chamber992 allow the second stream of carbonized catalyst to enter into thechamber 992. Consequently, the chamber 992 is in downstreamcommunication with the second carbonized catalyst conduit 452. Thesecond carbonized catalyst conduit 452 feeds the second carbonizedcatalyst stream to the space 996. The second carbonized catalyst streampasses along the wall 994 of the chamber 992 until it passes from thespace 996 through openings 998 into the chamber 992 impelled byfluidizing gas from distributor 919. The second carbonized catalyststream may enter the chamber 992 through openings 998 at a velocity inthe range of about 1 m/s (3 ft/s) to about 9.2 m/s (30 ft/s) and flux inrange of about 244 kg/m²/s (50 lb/ft²/s) to 1464 kg/m²/s (300lb/ft2/sec). The first stream of regenerated catalyst mixes with thesecond stream of carbonized catalyst in the chamber 992. The mixedstream of catalyst exits the opening 9110 in the chamber 992 and entersthe upper section 17 of the riser 910. The mixed stream of catalyst thentravels upwardly in the riser 910 to be contacted with feed. In anaspect, the opening 9110 may be at an elevation above a lower mostportion, and preferably an upper most portion, of the inlet 415. Hence,the first stream of regenerated catalyst may pass upwardly from theinlet 415 of the first catalyst conduit 412 into the chamber 492 to theopening 9110. In another aspect, the openings 998 may be at an elevationabove a lower most portion, and preferably an upper most portion, of aninlet 497 of the second carbonized catalyst conduit 452 to the riser910. As a result, the second stream of carbonized catalyst may passupwardly from the second catalyst conduit 452 into the chamber 992through space 996. The opening 9110 demarks an upper boundary betweenthe chamber 992 and the riser 910.

FIGS. 10 and 11 illustrate a further alternative embodiment of FIG. 4 inwhich a chamber 1092 extends from an enlarged lower section 1011 of ariser 1010, through a transition section 1013 and ascends to an uppersection 1017. FIG. 11 is a plan sectional view of segment 11-11 taken inFIG. 10. Elements in FIG. 10 with the same configuration as in FIG. 4will have the same reference numeral as in FIG. 4. Elements in FIG. 10which have a different configuration as the corresponding element inFIG. 4 will have the same reference numeral but be preceded with thedigit “10”.

The embodiment of FIG. 10 has a similar configuration as the embodimentof FIG. 4. The first regenerated catalyst stream from the firstregenerated catalyst conduit 1012 through the inlet 1015 and the secondcarbonized catalyst stream from the second carbonized catalyst conduit1052 through the inlet 1097 fluidized by gas from distributor 1019 mixin the enlarged lower section 1011 of the riser 1010 and both streamsenter into the chamber 1092 through an opening 1098 in the bottom of thechamber 1092 to be mixed further. In an aspect, the opening 1098 in thechamber 1092 is not in a vertical wall 1094 but may be in a bottom ofthe chamber 1092. The chamber 1092 extends from the enlarged lowersection 1011 to the upper section 1017 of the riser 1010. The wall 1094of the chamber 1092 is spaced from a wall 1090 of the enlarged lowersection 1011 to provide a space 1096.

Fluidizing gas from distributor 1019 impels the first regeneratedcatalyst stream and the second carbonized catalyst stream to passupwardly in the lower section 1011 from the first regenerated catalystconduit 1012 and the second carbonized catalyst conduit 1052,respectively, into the chamber 1092.

At least one helical swirl vane 142 in the chamber 1092 imparts anangular momentum to the mixture of the first regenerated catalyst streamand the second carbonized catalyst stream as they travel up through thechamber 1092 to further mix the two streams into a mixed catalyststream. The swirl vane may be placed anywhere along the height of thechamber 1092, but FIG. 10 shows it in the enlarged lower section 1011before the transition section 1013.

FIGS. 10 and 11 together show at least one baffle 140 in the space 1096between the wall 1090 of the riser 1010 and the wall 1094 of the chamber1092. The at least one baffle 140 prevents comingling of first stream ofregenerated catalyst and the second stream of carbonized catalyst in apotentially stagnant annular region above the entrances of the firstregenerated catalyst conduit 1012 and the second carbonized catalystconduit 1052 to the enlarged lower section 1011 of the riser 1010, thuspreventing calcination of the coke on the carbonized catalyst that maybe caught in the stagnant region. Alternatively, a baffle (not shown)may prevent any material from ascending in the space 1096 in thetransition section 1013 or the riser 1010 may be fashioned without someor all of the transition section 1013.

In this embodiment, the first regenerated catalyst stream from the firstregenerated catalyst conduit 1012 and the second carbonized catalyststream from the second carbonized catalyst conduit 1052 are both passedto the chamber 1092. The first regenerated catalyst conduit 1012 and thesecond carbonized catalyst conduit 1052 are both in upstreamcommunication with the enlarged lower section 1011 of the riser 1010 andthe chamber 1092. The first regenerated catalyst conduit 1012 feeds thefirst regenerated catalyst stream through inlet 1015 and the secondcarbonized catalyst conduit 1052 feeds the second carbonized catalyststream through the inlet 1097 to the enlarged lower section 1011 of theriser 1010 and to a space 1096 between a wall 1090 of the enlarged lowersection 1011 of the riser 1010 and the wall 1094 of the chamber 1092. Inan aspect, the opening 1098 may be at an elevation above a lower mostportion of the inlet 1015. In another aspect, the opening 1098 may be atan elevation above a lower most portion of an inlet 1097 of the secondcarbonized catalyst conduit 1052 to the riser 1010. Hence, the firststream of regenerated catalyst may pass upwardly from the inlet 1015 ofthe first catalyst conduit 1012 and the second stream of carbonizedcatalyst may pass upwardly from the inlet 1097 of the second catalystconduit 1052 to the opening 1098 into the chamber 1092.

The first regenerated catalyst stream and the second carbonized catalyststream pass into the chamber 1092 from the space 1096 and the enlargedlower section 1011 of the riser 1010 Consequently, the chamber 1092 isin downstream communication with the first regenerated catalyst conduit1012 and the second carbonized catalyst conduit 1052. The first streamof regenerated catalyst mixes with the second stream of carbonizedcatalyst in the enlarged lower section 1011 and mix further in thechamber 1092 due to the angular momentum imparted to the catalyststreams upon passing the at least one and preferably a plurality ofswirl vanes 142. The mixed catalyst stream exits an opening 10110 in atop of the chamber 1092 and enters the upper section 1017 of the riser1010. The mixed stream of catalyst then travels upwardly in the riser1010 to be contacted with feed. The opening 10110 demarks an upperboundary between the chamber 1092 and the riser 1010. Alternatively,tops 144 of the swirl vanes 142 may be viewed as an upper boundary ofthe chamber 1092.

EXAMPLE

We conducted Computational Fluid Dynamics modeling to determineperformance of different embodiments of the present invention. The firstregenerated catalyst stream was devoid of coke, had a catalyst flow rateof 8,647,893 kg/h (19,065,343 lb/hr), a gas flow rate of 11,674 kg/hr(25,738 lb/hr) and a temperature of 742° C. (1,367° F.). The secondcarbonized catalyst stream was fully coked indicating a cokeconcentration of 0.858 wt-% of catalyst, also had a catalyst flow rateof 8,647,893 kg/h (19,065,343 lb/hr), a gas flow rate of 10,810 kg/hr(23,833 lb/hr) and a temperature of 549° C. (1,020° F.). The catalystand gas properties in Table I were also utilized in the model.

TABLE I Property Metric English Catalyst Density 1442 kg/m³ 90 lb/ft³Gas Density 1.041 kg/m³ 0.065 lb/ft³ Gas Viscosity 0.014 cP GasConductivity 0.024 W/m-K 0.014 Btu/h-ft-° F. Catalyst Conductivity 0.100W/m-K 0.58 Btu/h-ft-° F. Gas Heat Capacity 1004.83 J/kg-K 0.24 Btu/lb-°F. Catalyst Heat Capacity 1151.370 J/kg-K 0.275 Btu/lb-° F.

For the embodiments in FIGS. 1, 2 and 3, the fluidizing steam rate was69,638 kg/hr (153,525 lb/hr) from the single distributor 16. For theembodiments in FIGS. 4, 5 c; 6; 7, 8 and 9, 6.1 wt-% or 4,535 kg/hr(10,000 lb/hr) of the steam from distributor 416, 716, 916 was divertedto the top distributor 419, 719, 919 to fluff the enlarged lower section11 of the riser 10. The steam temperature was 154° C. (310° F.).

Based on these parameters, modeling indicated the embodiments of theinvention would yield the temperature differentials as reported in TableII.

TABLE II Figure(s) Illustrating Embodiment 1, 2 3 4, 5c 6 7, 8 9Temperature 4 0.8 13.6 119  76 29 Differential, ° C. (° F.) (7) (1.5)(24.5) (214) (136) (53)

Temperature differential was calculated at a location in the riser 10, 1meter (3.3 feet) below the feed distributors 18, which in the modeledriser 10 was in the upper riser 17 above the transition section 13. Thetemperature differential represents the maximum temperature spread forthe catalyst, typically the difference of the hottest regeneratedcatalyst and the coolest carbonized catalyst. The embodiments in FIGS.1, 2 and 3 showed the best performance in terms of catalyst mixing whichproduced essentially homogeneous catalyst temperature.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention. Itshould be understood that the illustrated embodiments are exemplaryonly, and should not be taken as limiting the scope of the invention.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing, all temperatures are set forth in degrees Celsius and,all parts and percentages are by weight, unless otherwise indicated.Pressures are given at the vessel outlet and particularly at the vaporoutlet in vessels with multiple outlets.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

The invention claimed is:
 1. A process for mixing two streams ofcatalyst comprising feeding a first stream of catalyst into a spacebetween a wall of a riser and a wall of a chamber in said riser; feedinga second stream of catalyst to said riser; passing said first stream ofcatalyst from said space into an opening in said chamber; passing saidfirst stream of catalyst and said second stream of catalyst up saidriser; and injecting a hydrocarbon feed into the riser.
 2. The processof claim 1 further comprising passing said first stream of catalystalong said wall of said chamber before said first stream of catalystenters into said opening.
 3. The process of claim 1 wherein said firststream of catalyst exits said chamber through said opening.
 4. Theprocess of claim 1 further comprising feeding said second stream ofcatalyst to said space.
 5. The process of claim 4 further comprisingpassing said second stream of catalyst from said space into said chamberthrough said opening in said chamber.
 6. The process of claim 5 furthercomprising passing said second stream of catalyst along said wall ofsaid chamber before said second stream of catalyst enters into saidopening.
 7. The process of claim 4 further comprising mixing said firststream of catalyst and said second stream of catalyst in said space. 8.The process of claim 6 further comprising mixing said first stream ofcatalyst and said second stream of catalyst in said chamber.
 9. Theprocess of claim 1 further comprising preventing catalyst from exitingthe top of the chamber in alignment with the riser.
 10. The process ofclaim 1 further comprising passing said first stream of catalyst fromsaid chamber into said space while imparting a swirling motion to saidfirst stream of catalyst as it passes from said chamber into said space.11. A process for mixing two streams of catalyst comprising feeding afirst stream of catalyst from a first catalyst conduit into a spacebetween a wall of a riser and a wall of a chamber in said riser; feedinga second stream of catalyst from a second catalyst conduit to saidriser; passing said first stream of catalyst from said space into anopening in said chamber; passing said first stream of catalyst and saidsecond stream of catalyst up said riser; and injecting a hydrocarbonfeed into the riser.
 12. The process of claim 11 further comprisingpassing said first stream of catalyst from said first catalyst conduitalong said wall of said chamber before said first stream of catalystenters into said opening.
 13. The process of claim 12 further comprisingfeeding said second stream of catalyst from said second catalyst conduitinto said space.
 14. The process of claim 13 further comprising passingsaid second stream of catalyst from said space into said chamber throughsaid opening in said chamber.
 15. The process of claim 14 furthercomprising passing said second stream of catalyst along said wall ofsaid chamber before said second stream of catalyst enters into saidopening.
 16. The process of claim 15 further comprising mixing saidfirst stream of catalyst and said second stream of catalyst in saidspace and in said chamber.
 17. The process of claim 11 furthercomprising preventing catalyst from exiting the top of the chamber inalignment with the riser.
 18. A process for mixing two streams ofcatalyst comprising passing a first stream of catalyst from a firstcatalyst conduit into a chamber in said riser; feeding a second streamof catalyst from a second catalyst conduit into a space between a wallof a riser and a wall of a chamber in said riser; passing said firststream of catalyst from said chamber into said space or passing saidsecond stream of catalyst from said space into said chamber through aplurality of openings in said chamber; and passing said first stream ofcatalyst and said second stream of catalyst up said riser.
 19. Theprocess of claim 18 further comprising passing said first stream ofcatalyst from said first catalyst conduit along said wall of saidchamber before said first stream of catalyst enters into said openingsand passing said second stream of catalyst from said second catalystconduit along said wall of said chamber before said second stream ofcatalyst enters into said openings.
 20. The process of claim 19 furthercomprising mixing said first stream of catalyst and said second streamof catalyst in said chamber and passing said mixed stream of said firststream of catalyst and said second stream of catalyst from said openingsinto said space.